Lots of questions! First off, venlafaxine isn't an SSRI. Citalopram's common side effects are mostly mild, though as with any medication, there's always the possibility of side effects that are more unpleasant or severe. The two drugs you're already taking, valproate and quetiapine, are also appropriate treatments for bipolar.   Since your doctor is proposing an antidepressant, I assume depression is your current problem. This suggests to me (but I'm not a doctor) that he hopes citalopram will make you less of a zombie, not more.   There's no predicting how any drug will affect your sleep cycle. While headache is a possible less common side effect, that doesn't mean a lot - after all headache is also a possible side effect of quetiapine.   Bipolar disorder does not go away. It runs in cycles. I'd venture to guess that it's the fact you have "up" periods that leads your doctor to suspect bipolar.   The bottom line is that you can't really know how a medication will affect you unless, for example, you have already taken a close relative of the drug and know you have an allergy. Your doctor should monitor your mood and health closely when prescribing an antidepressant, as sometimes it can lead to hypomania or mania developing.